This invention relates to a digital video effects apparatus.
In the digital effects apparatus that is sold by The Grass Valley Group, Inc. under the trademark Kaleidoscope, it is possible to apply certain effects only to selected areas of the video field. For example, effects that are known as input recursive effects, bitmap effects, mosaics and defocus can be applied in predetermined areas of the field. The area in which the selected effect does not take place is defined by a mask signal, which is off (logical 0) where the effect is to be inhibited and is on (logical 1) where the effect is to be allowed.
The Kaleidoscope video effects apparatus operates in the shaped video domain, in which a video signal is multiplied by an associated crop (or key) signal that defines an area of the video field. The crop signal may, for example, be generated by a luminance key generator or a rectangle generator that forms part of the video effects apparatus. In some effects (mosaics and defocus) the crop signal is used as the mask signal because it allows use of a luminance key signal or a rectangle signal to define the area over which the effect is inhibited. However, in order to preserve the crop information for subsequent use, e.g. unshaping the video signal, it is necessary for a device that uses the crop signal as a mask signal to regenerate the crop signal. Input recursive and bitmap effects employ mask signals that are different from the crop signal, and therefore do not necessitate regeneration of the crop signal.